(a) Field of the Invention
The present invention relates to a mobile communication system, and more particularly, to an apparatus and method of estimating a channel based on a channel delay spread.
(b) Description of the Related Art
In a wireless environment, a channel is subjected to multipath fading due to ambient obstacles and a Doppler shift due to a speed of a moving body. Here, multipath fading means that electromagnetic waves are synthesized in a state where phases of the electromagnetic waves are different from each other due to multiple reflections and are received. The Doppler shift means that the environment is changed to a fast fading environment where the intensity of an electric wave temporally quickly varies when moving at a high speed, and a frequency shift due to a Doppler effect becomes severe in terms of a frequency. In this case, delay spread due to the multipath causes frequency selective fading, and when the delay spread increases, a channel correlation between subcarriers decreases. This means that channels between the subcarriers vary on a large scale.
Therefore, in order to securely estimate a channel that corresponds to a large delay spread, a method is used in which pilot subcarriers are arranged simply. However, if this method is used, a data transmission rate decreases. Further, in order to estimate the channel, it is required to perform an inverse matrix operation that is very complicated. As a result, it becomes difficult to implement an apparatus for estimating a channel.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.